Preparation Of Cathode Electrocatalysts In Fuel Cell Containing Nitrogen-doped Porous Carbon And Their Properties

Energy problem is one of the biggest problems in twenty-first Century. Along with the increase of population and development of economy, the energy demand is increasing. More and more scientific researchers who have spared no effort to find sustainable energy equipment, such as fuel cells, solar battery, metal-air battery, lithium ion battery, super capacitor and so on. Among them, the fuel cell as an environmentally friendly energy equipment, has been widely concerned. However, in the process of commercial application of fuel cells, one of the biggest problem encountered is the cathodic catalyst of oxygen reduction reaction. In view of this problem, this paper studies two kinds of new oxygen reduction catalysts, which have low cost and high performance, can effectively catalyze the reduction reaction of oxygen in the fuel cell. The main work is as follows:Preparation of cobalt and nitrogen Co-doped mesoporous carbon/graphene nanocomposite (CMK3/G-N-Co):We used a modified Hummers method to prepared the graphene oxide, then add mesoporous carbon CMK3 and cobalt(II) acetate tetrahydrate to the prepared graphene oxide solution. They were mechanically agitated and freeze dried. The dried mixture was heated treatment in the ammonia atmosphere and the final product was obtained. The final product was characterized by Scanning transmission electron microscopy, X-ray diffraction and photoelectron spectroscopy. The catalytic performance of the final product was tested in acid and alkaline media. We explored the effect of the content of cobalt(II) acetate tetrahydrate, the content of graphene oxide, heat treatment temperature and time on the catalytic activity of CMK3/G-N-Co catalyst. The optimum preparation conditions were as follows:the content of cobalt(Ⅱ) acetate tetrahydrate was 13.0 mg, the content of graphene oxide was 30.0 mL, heat treatment temperature was 950℃, heat treatment time was 50 min. The product prepared by the method shows excellent catalytic ability in alkaline media for the oxygen reduction reaction and the half-peak potential is only 27 mV less than that of the commercial 20% Pt/C catalyst. The product revealed superior stability and tolerance to methanol poisoning effects compared to the commercial 20% Pt/C catalyst.Preparation of iron and nitrogen Co-doped mesoporous carbon/carbon nanotubes nanocomposite (NFe-CNT/CMK3):The mesoporous carbon CMK3 and ferric chloride were dissolved in deionized water, then which were mechanically agitated and freeze dried. The dried mixture and 500 mg melamine were mixed by grind process. Then the mixture was heated treatment in the nitrogen atmosphere and the final product was obtained. The final product was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET specific surface area test. The catalytic performance of the final product was tested in acid media. We explored the effect of the content of ferric chloride, heat treatment temperature and time on the catalytic activity of NFe-CNT/CMK3 catalyst. The optimum preparation conditions were as follows:the content of ferric chloride was 6.0 mg, heat treatment temperature was 950℃, heat treatment time was 60 min. The product prepared by the method shows excellent catalytic ability for the oxygen reduction reaction in acidic media. The value of the onset potential and half-peak potential of the product is only 68 mV and 63 mV less than that of the commercial 20% Pt/C catalyst, respectively. When the potential is lower than 670 mV, the reduce current of the product is remarkably larger than that of commercial 20% Pt/C. The product also reveals superior stability and tolerance to methanol poisoning effects compared to 20% Pt/C.